For a top down shooting game, how do i do different enemy wave formations/styles. Like i would have 1 type formation spawn a bunch of random enemies that go top to bottom, and another that spawns them in military formation, or another that has a few enemies revolving around a central object while moving top to bottom.

How id do it is, you could create either a single sprite, drop and arrange it in the formations you would like off-screen and for each of that sprite you could spawn an enemy. For you different waves you could rearrange these images.

Or a single large sprite (for each formation) with multiple image points.